According to the 36331 protocol, when a Radio Resource Control (RRC) connection reconfiguration message received by the user equipment (UE) comprises mobility control information and when the inter-frequency switching or inter-frequency RRC connection reconstruction is performed, the UE will perform the following actions:
1> if the signal element of measurement object identification list (measObjectIdList) in the measurement configuration (VarMeasConfig) stored at the UE side has a measurement object identification (measObjectId) corresponding to the destination side cell (referred to as the D side cell) frequency point;                2> for each measurement identification (measId) corresponding to the measurement identification list (measIdList);                    3> if the measObjectId connected with the measId is the source side cell (referred to as the S side cell) carrier frequency;                            4> connect the measId to the measObjectID corresponding to the D side cell carrier frequency;                                    3> if the measObjectId connected with the measId is the D side cell carrier frequency;                            4> connect this measId to the measObjectId corresponding to the S side cell carrier frequency;                                                
1> if the signal element of measObjectIdList in the VarMeasConfig does not have a measObjectId corresponding to the D side cell frequency point
2> delete the measId of all the measObjectId connected to the S side cell carrier frequency;
. . .
1> if the received RRC connection reconfiguration message includes the measConfig;
2> execute the measurement configuration in the RRC connection reconfiguration message;
Herein, this action is called the Swap action, from the protocol, it can be seen that it is the mandatory action for the inter-frequency switching and the inter-frequency RRC connection reconstruction. Table 1 and Table 2 show the measurement configuration examples before and after the UE performs the Swap action. The first cell and the second cell are inter-frequency neighboring cells, the UE initially accesses the first cell, at this time, the measurement configuration of the UE is the same as the measurement configuration of the first cell. When performing the inter-frequency switching or the inter-frequency RRC connection reconstruction, the UE performs the aforementioned Swap action. The second cell performs the Swap action on the measurement configuration sent from the first cell and saves it so that the UE measurement configuration can be guaranteed to be consistent with the measurement configuration at the second cell side, the RRC connection reconfiguration message does not send the measurement configuration, which reduces the XI interface signaling transmission between the base station and the UE.
TABLE 1an example of the measurement configuration saved by the UEbefore the inter-frequency switching and theinter-frequency RRC connection reconstructionMeasIDMeasObjectIDReportConfigID112 (A2)214 (ANR)325 (A3)435 (A3)598 (B2)
TABLE 2an example of the measurement configuration after the UE performsthe Swap on the measurement configuration after the inter-frequencyswitching and the inter-frequency RRC connection reconstructionMeasIDMeasObjectIDReportConfigID122 (A2)224 (ANR)315 (A3)435 (A3)598 (B2)
The aforementioned method can reduce the XI interface signaling and improve the system efficiency, but it does not take into account the D side cell configuration, therefore, there are problems appear in the following circumstances:
suppose that there exist three cells, cell—0 takes the celli and the cell—2 as its neighboring cells, the frequency points of the three neighboring cells are not the same, the UE initially accesses the cell—0, and accesses the cell—1 by inter-frequency switching\inter-frequency RRC connection reconstruction.
If the cell—1 does not take the cell—0 as its neighboring cell, it does not take the cell—0 frequency point as the inter-frequency point in configuration. After the switching or the RRC connection reconstruction, all the inter-frequency measurement events aiming to the cell—0 frequency point are unreasonable, this is because the cell—1 does not take the cell—0 as its inter-frequency neighboring cell, and it should not configure measurement events related to the cell—0 frequency point.
If the Evolved Node B (eNB) in which the cell—0 is located supports the Automatic Neighbor Relation (ANR) function and is configured with the measurement events; the eNB of the cell—1 does not support the ANR function and is not configured with the measurement event; after the switching or the RRC connection reconstruction, the measurement configuration of the cell—1 has the measurement configuration that does not support the ANR function, but it is unreasonable for configuring the UE with the measurement configuration which does not ought to be existed.
If the cell—1 does not take the cell—2 as its neighboring cell, it does not take the cell—2 frequency point as an inter-frequency point in configuration. After the switching or RRC connection reconstruction, all inter-frequency measurement events aiming to the cell—2 frequency point are unreasonable.
If the cell—0 does not support the Inter Cell Interference Coordination (ICIC) function while the cell—1 does, and it needs to send the ICIC related measurement events to all the UEs accessing the cell—1 to solve the problem of same frequency interference, since the cell—0 does not configure the UE with the ICIC related measurement events, after the switching or the RRC connection reconstruction, the UE does not have the ICIC related measurement events, which does not achieve the objective of avoiding the same frequency interference by the cell—1 sending the ICIC to all the UEs accessing the cell—1.
The aforementioned four scenarios can lead to that the UE is lack of measurement configuration or the measurement configuration is not available after the inter-frequency switching or the inter-frequency RRC connection reconstruction, the same SWAP action made by the base station as that made by the UE can only solve the problem of configuration consistence, but it cannot guarantee the accuracy of the measurement configuration.